LineTo函数在mousemove中怎么能在移动过程中只有一条线(50分)

要求测距，现在mousemove中使用LineTo函数来画线，鼠标移动后会出现无数条线，怎么能让将前一个鼠标点的线去掉，只需要当前鼠标点的这条线就可以了<br>procedure TForm1.MouseMove(Sender: TObject; Shift: TShiftState; X,<br> &nbsp;Y: Integer);<br>begin<br> &nbsp; &nbsp; MoveToEx(m_lngMapDc,ScrX,ScrY,TmpPoint);<br> &nbsp; &nbsp; LineTo(m_lngMapDc,X,Y);<br>end;

你设一组全局变量，目的是纪录每次划线的前一条线的坐标，然后你在每次划线的时候先清除前一条线

画方框的代码，不想改了，你自己改改<br><br>var<br> &nbsp;MouseButtonDown: Boolean;<br> &nbsp;Rect: TRect;<br>//mousedown<br> &nbsp; &nbsp;MouseButtonDown := True;<br> &nbsp; &nbsp;Screen.Cursor := crCross;<br> &nbsp; &nbsp;with Rect do<br> &nbsp; &nbsp;begin<br> &nbsp; &nbsp; &nbsp;Left := x;<br> &nbsp; &nbsp; &nbsp;Top := y;<br> &nbsp; &nbsp; &nbsp;Right := x;<br> &nbsp; &nbsp; &nbsp;Bottom := y;<br> &nbsp; &nbsp;end;<br>//mousemove<br> &nbsp; &nbsp;if MouseButtonDown then<br> &nbsp; &nbsp;begin<br> &nbsp; &nbsp; &nbsp;Panel1.Canvas.DrawFocusRect(Rect);<br> &nbsp; &nbsp; &nbsp;with Rect do<br> &nbsp; &nbsp; &nbsp;begin<br> &nbsp; &nbsp; &nbsp; &nbsp;Right := x;<br> &nbsp; &nbsp; &nbsp; &nbsp;Bottom := y;<br> &nbsp; &nbsp; &nbsp;end;<br> &nbsp; &nbsp; &nbsp;Panel1.Canvas.DrawFocusRect(Rect);<br> &nbsp; &nbsp;end;<br>//mouseup<br> &nbsp; &nbsp;MouseButtonDown := False;<br> &nbsp; &nbsp;Screen.Cursor := crdefault;

解决了，呵呵，刷新一下就好了，它自己会没掉的

多人接受答案了。